Note: Descriptions are shown in the official language in which they were submitted.
CA 02659080 2009-01-20
WO 2008/024641
PCT/US2007/075708
DISCRETE LEAK DETECTION DEVICE AND METHOD
This invention includes a device and method for detecting the presence of one
or
more targeted liquids in volume of space where the targeted liquid is not
normally
present.
BACKGROUND OF THE INVENTION
Transporting liquids such as crude oil, refined petroleum products, or
corrosive
liquids such as concentrated acids or bases is often accomplished utilizing
tanks and
underground pipelines. Underground pipelines are subject to leakage from the
piping,
fittings, and valves. When an underground pipe carrying a hazardous or
corrosive liquid
develops a leak, the leak must first be detected and located before it can be
repaired.
Various systems for detecting leaks are well-known. For example, sensor cables
may be used to detect changes in variables along an elongate path, such as the
presence
of a liquid such as water, an organic solvent, or a corrosive liquid. Sensor
cables may be
extended in a pipeline, along the length or longitudinal axis or at various
sections or
points at which the leakage of liquids tends to occur. Additionally, crude oil
leak
detection over the many thousands of miles of an oil pipe transport system is
extremely
difficult to perform. However, detecting low rate leaks caused by corrosion of
the carrier
pipe (inner pipe) is increasingly important to the oil companies and
governmental
agencies, such as the State of Alaska, as the piping system ages.
Accordingly, there is a need in the field of transporting liquids for
improvements
in leak detection. The present invention addresses this and other needs.
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BRIEF SUMMARY OF THE INVENTION
The present invention includes a fluid detection device having an attachment
means for
fixing the device to a surface, the attachment means forming a passage thought
the
surface, a discriminating sensor device effective to differentiate between a
target fluid
and a non-targeted fluid, a source of power and an indicator for indicating
the presence of
the target fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGs. 1A-1D illustrate a preferred embodiment of the invention;
FIGs. 2A-2B illustrate examples of sensors components of the invention;
FIG. 3 illustrates an attachment mechanism for the invention;
FIGs. 4A-4B illustrate simple dual mode enunciation systems of the invention;
and,
FIGs. 5A-5C illustrate the invention having the power and enunciation
functions
performed remotely.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention preferably includes a device having an attachment means or
device,
a discriminating sensor device that can differentiate between the target fluid
and a non-
targeted fluid (e.g., water), a source of power; and an indicator. The
invention may
further include a method using the above-described device where the method
assures that
the targeted fluid will come into contact with the sensor device.
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One preferred embodiment of the invention is shown in Figs. 1A-1D. As seen in
Figs. 1A and 1B, the device 7 includes an attachment having two or more tangs
2 with
barbed points 4, and a soft compressible and resilient washer 3. The device 7
is attached
to and placed though a surface in a two part operation using a mounting collar
6 and the
body 5 of the device 7. This method is especially suited to attaching the
device to a thin
layer of material as for instance sheet metal 1. The sheet metal 1 may have a
soft or
deformable insulation material on the surface of the sheet metal 1 opposite
the device 7.
To use this method of attachment, the installer will drill a hole 6 of the
appropriate
diameter through the sheet metal 1. The device 7 is then installed by pushing
the tang
end 2 of the device 7 through the hole 6 such that the barbs 4 extend beyond
the edge of
the sheet metal 1 and latch the device 7 into place. The thick washer 3 of a
soft but
resilient material, closed cell silicone foam for instance, is fitted to the
device 7 so that
during the installation, the washer 3 is compressed between the surface of the
sheet metal
1 and the body of the mounting collar 6. After the barbs 4 latch behind the
inner surface
of the sheet metal 1, the tendency of the deformed washer to re-expand serves
to pull
back against the barbs 4 and insure a snug fit at a predictable depth.
Referring to Figs. 1C and 1D, the body 5 of the device 7 can next be threaded
into
the threads at the bottom of the mounting collar 6. A tubular extension 8 of
the sensor
chamber can be sized such that with the body 5 of the device 7 in place, the
barbs 4 are
completely extended in a radial direction and locked into place and are
incapable of
bending inward. This feature assures a positive locking mechanism and allows
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substantial weight to be suspended up to the breaking point of barbs 4, tangs
2 or yield
strength of the sheet metal 1. This feature is particularly helpful if the
area above the
sheet metal 1 is filled with a semi-rigid, but deformable, foam insulation
such as
polyurethane.
Referring to Figs. 2A and 2B, the sensor device (shown in Fig. 2A) 9 is
fabricated
at the end of a printed circuit board. The sensor element 10 has a film of
material that
changes resistance in the presence of the targeted fluid. In this embodiment,
the film is a
thin layer of carbon particles suspended in a polymer binder such that the
carbon particles
make contact with each other and produce a lower resistivity when the target
fluid is not
present. When the target fluid is present the polymer binder material can be
formulated
to swell, thereby reducing the quantity of carbon particles touching each
other and
secondarily causing a dramatic change in resistivity through the film. Other
geometries
of carbon/polymer films are determinable by one skilled in the art, such as
the deposition
of the carbon/polymer film on the exterior surface of a tubular, leaded
component such as
for instance a 1 watt carbon resistor, shown in Fig. 2B.
In both of these embodiments and similar embodiments, the sensor device 9 can
be constructed and assembled into the body 5 of the device 7 such that the
senor element
extends up to and within the tubular extension 8 of the device 7. It is
possible to seal
the lower portion of the tubular extension 8, for instance with epoxy potting
compound,
such that a chamber closed on the bottom but open on the top is formed. In the
initial
embodiment, with the device attached to the bottom side of a pre-insulated
crude oil
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pipeline, a drip chamber is formed such that any oil leaking from the primary
pipe and
flowing along the inside of the insulation's sheet metal cladding, will drip
into the tubular
extension 8 of the device 7 and into direct contact with the sensor element
10.
The sensor technology sited in this preferred device has the special property
of
discriminating between a fluid of interest, as for example crude oil, and
water. It is
important to ignore water since water can frequently be present due to
condensation or
imperfect sealing of the insulation cladding or lagging.
An additional aspect of the invention utilizes other discriminating sensors in
other
double wall pipe or double bottom tank systems where a targeted fluid should
be detected
but water should be ignored. An example of another discriminating sensor is
the acid
sensor disclosed in United States Patent No. 6,777,947, by McCoy et. al.,
entitled "Sensor
Cable", issued August 17, 2004. In this example the targeted fluid would be
concentrated
acid. The outer wall of a typical double wall hazardous fluid pipe system
would provide
the mechanism to convey any leak to the body of the device. The means of
attachment
and the use of the tubular extension acting as a drip chamber would be
identical.
The means of attachment is not limited to the tang, barb and locking mechanism
as described above. For example, in situations where the wall thickness of the
containment pipe or exterior tank bottom is sufficiently thick, a threaded
mechanism 11
with an o-ring seal 12 may prove equally effective. Such an arrangement is
shown in Fig.
3.
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The invention preferably includes a power supply 15. Representative power
supplies include batteries of sufficient shelf life and charge storage
capacity as an ideal
means of powering a self contained version of the device. As an example, the
19 amp-
hour, 3.6 VDC Lithium Thyonil D-cell, Model TL-5930 manufactured by Tadrian
Lithium Batteries has excellent shelf life characteristics and high energy
density. Using
the carbon / polymer thin film sensor technology the resistance of the sensor
film can be
monitored with an extremely low current such that the standby life of the self-
contained
device is projected to be in excess of 5 years. If and when the polymer film
is contacted
by a target fluid, such as crude oil, the remaining residual battery power can
be utilized to
activate one or several enunciation devices. The initial embodiment of the
device is sized
to enclose the thin film sensor device, circuit board space 13 for the
components for
monitoring the resistance of the sensor, and one or more simple enunciation
devices.
The indicator or method of enunciation of the invention indicates that a
targeted
fluid has been detected. In one embodiment of the device, the method of
enunciation
includes high brightness, high efficiency LEDs 16. As seen in Figs. 1C and 1D,
the
lower cover 17 (shown in Fig. 4B) of the enclosure system is fabricated from a
clear
polymer material so that the LEDs 16 (shown in Fig. 4A) can be seen through
the clear
cover. The circuitry of the device can be easily made to intermittently flash
the LEDs 16
when the resistance of the sensor film exceeds a pre-set threshold. In this
embodiment,
"no flashing" indicates that no target fluid has contacted the device, while
flashing LEDs
16 indicate that the target fluid has contacted the sensor portion of the
device. Very low
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duty cycle pulsing can be effective as enunciation and is very conservative of
battery
power. For instance a flash lasting 50 milliseconds emitted once every second,
can be
easily detected by a near-by observer while consuming only 5% of the energy
required to
operate the LEDs continuously.
Other examples of battery powered enunciation devices include low power FM
transmitter or a radio frequency node of a mesh network.
As seen in Figs. 4A and 4B, an example of a simple dual mode enunciation
system is illustrated. The device is shown to be made to flash the LEDs 16 and
transmit a
low power FM signal by an FM transmitter 14. In this example a maintenance
worker
driving along a service road would be able to see a flashing indication if the
device has
detected a leak. Using a vehicle mounted FM radio receiver, the worker would
be able to
hear a tone or a pulsed signal when in the vicinity of a device that had
detected the target
fluid.
Initial analysis of the circuitry necessary to monitor the sensor film, flash
the
LEDs and emit an FM signal indicates that the battery capacity may be
sufficient for an
enunciation lasting in excess of 30 days from initial detection of the
targeted fluid when
the TL-5930 battery is used.
As seen in Figs. 5A, 5B and 5C, this embodiment of the invention has the power
and enunciation functions performed through a direct wire connection to
control room
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equipment. The output of the sensor circuit 18 may easily be configured to
close a solid
state switch (e.g., a transistor) when the target fluid is detected. A switch
closure 19 can
be detected and located along a four wire circuit in the method taught by
United States
Patent No. 5,235,286, to Masia et. al., entitled "Method for Detecting and
Obtaining
Information about Changers in Variables", issued August 10, 1993.
A device of this type is useful when physical inspection is not easily
achieved.
Representative uses of the invention include monitoring pipeline systems
preferably
having a multiple wall system (e.g., having an inner pipe with an outer
protective layer).
These systems are commonly found in above ground pre-insulated pipes such as
oil
piping systems found on the north slope of Alaska having a steel pipe interior
within a
polyurethane foam filled shell. The control room device, for example, Tyco
Thermal
Controls device TT-SIM can be simply modified to produce sufficient current to
power in
excess of 100 detection devices. The circuit embodied in the TT-SIM can also
locate
which device along the string of 100 or more devices made the detection and
can report
the distance from the control room to the detection device in terms of feet or
meters.
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